1. Introduction

In this tutorial, we will explore how to handle control flow in Kotlin. Control flow refers to the order in which the program's code executes. We will delve into the syntax and usage of various control flow structures in Kotlin, such as conditional statements and loops.

By the end of this tutorial, you'll be able to:
- Understand and use conditional statements (if, when)
- Understand and use loops (for, while, do-while)
- Use break and continue statements

To get the most out of this tutorial, you should be comfortable with basic programming concepts and have a basic understanding of Kotlin syntax.

2. Step-by-Step Guide

2.1 Conditional Statements

In Kotlin, conditional statements are used to make decisions based on different conditions. The two main conditional statements in Kotlin are if and when.

If Statement

The if statement is the most basic control flow statement. It decides which statement to execute based on a Boolean condition.

Syntax:

if (condition) {
  // code to be executed if the condition is true
} else {
  // code to be executed if the condition is false
}

When Statement

The when statement in Kotlin is like the switch statement in other languages. It selects one of many code blocks to be executed.

Syntax:

when (variable) {
  case1 -> // code to be executed if variable matches case1
  case2 -> // code to be executed if variable matches case2
  else -> // code to be executed if none of the cases match
}

2.2 Loops

Loops are used to execute a block of code repeatedly. Kotlin provides several loops: for, while, and do-while.

For Loop

The for loop iterates through anything that provides an iterator. Here's the basic syntax:

for (item in collection) {
  // code to be executed
}

While Loop

The while loop executes a block of code repeatedly as long as the condition is true.

Syntax:

while (condition) {
  // code to be executed
}

Do-While Loop

The do-while loop is similar to while loop except that the condition is evaluated after the execution of the block of code. Therefore, a do-while loop executes the block of code at least once.

Syntax:

do {
  // code to be executed
} while (condition)

3. Code Examples

3.1 Conditional Statements

If Statement

val number = 7

if (number > 10) {
  println("Number is greater than 10")
} else {
  println("Number is not greater than 10") // This will be printed
}

When Statement

val score = 85

when {
  score >= 90 -> println("Excellent")
  score >= 80 -> println("Good") // This will be printed
  else -> println("Not bad")
}

3.2 Loops

For Loop

for (i in 1..5) {
  println(i) // This will print numbers 1 to 5
}

While Loop

var i = 1

while (i <= 5) {
  println(i) // This will print numbers 1 to 5
  i++
}

Do-While Loop

var i = 1

do {
  println(i) // This will print numbers 1 to 5
  i++
} while (i <= 5)

4. Summary

In this tutorial, we learned about control flow in Kotlin. We covered conditional statements (if, when) and loops (for, while, do-while). To master these concepts, practice is key. Try to incorporate these structures in your Kotlin projects.

To further your understanding, you can check out Kotlin's official documentation on control flow: Kotlin Control Flow

5. Practice Exercises

1. Write a Kotlin program that prints the factorial of a number.

2. Write a Kotlin program that checks if a number is prime or not.

3. Write a Kotlin program that prints the Fibonacci series up to a given number.

Here's the solution to the first exercise:

fun factorial(n: Int): Long {
  var result = 1L
  for (i in 2..n) {
    result *= i
  }
  return result
}

fun main() {
  val num = 5
  println("Factorial of $num = ${factorial(num)}") // Factorial of 5 = 120
}

In this code, we define a function that calculates the factorial of a number. We then call this function with a number to get the factorial.